a(n) is the number of perfect matchings in the graph with vertices labeled 1 to 2n with edges {i,j} for 1<=|i-j|<=4.
A320346
a(n) is the number of perfect matchings in the graph with vertices labeled 1 to 2n with edges {i,j} for 1<=|i-j|<=4.
Terms
- a(0) =1a(1) =1a(2) =3a(3) =12a(4) =35a(5) =105a(6) =329a(7) =1014a(8) =3116a(9) =9610a(10) =29625a(11) =91279a(12) =281303a(13) =866948a(14) =2671727a(15) =8233671a(16) =25374513a(17) =78198928a(18) =240992592a(19) =742688720a(20) =2288811009a(21) =7053635369a(22) =21737825143a(23) =66991419284a(24) =206453506615a(25) =636246416105
External references
- oeis: A320346